In the field of feeding a strip of ferrous metal from a supply coil to a reciprocating press which may cut or deform the strip at progressive intervals, it is common to feed the strip from the supply coil through a strip straightening device or rolls which are continuously driven. After the strip is straightened, it is fed in a step-by-step manner or incrementally by a stock feeder to the reciprocating press. Usually, an accumulation loop is formed within the strip between the continuously operating strip straightening rolls and the incremental stock feeder to accommodate the difference in strip feed rates.
For example, U.S. Pat. No. 2,025,418 discloses a loop forming device which incorporates a series of rollers for guiding or directing a continuously feeding strip along a path to form a U-shaped loop. Similarly, U.S. Pat. No. 3,888,400 discloses a series of guide rollers which direct the strip into a U-shaped accumulation or storage loop. In the loop forming devices disclosed in each of these patents, the leading end of the strip must be threaded or fed through the device, and the strip guide rollers must be properly lubricated or maintained so that no significant dragging or restraining force is applied to the strip as it is fed longitudinally through the device.
Another type of loop forming device is disclosed in U.S. Pat. No. 3,784,071 wherein an accumulation loop is formed within a strip between the opposing runs of two endless belt conveyors. A set of magnets are used to hold the strip against the conveyor belts to avoid slippage of the strip relative to the belts which are independently driven by variable speed motors. While this structure avoids the necessity for feeding or threading the leading end of the strip through the loop forming device, the structure is relatively complex and expensive in construction when compared to the loop forming devices incorporating strip guide rollers.